Heterodyning horn



Oct. 14, 1930..

B. AMES HETERODYNING HORN Filed July 20, 1.927

Shee'ts-Sheet l Oct. 14, 1930. B, AMES 1,778,206

HETERODYNING HORN Filed July 20, 1927 2 Sheets-Sheet 2 'lll'.lll 'Illllll Llllllllllllr//llllf Patented Oct. 14, 1930 PATENT. OFFICE :BUTLER sans, or LOWELL, MASSACHUSETTS [Hartaanval-Ne :acari` Application filed. July 20, 1927. Serial No. 207,162.

This invention relates to a' sound-producing means and more articularly to a signaling device designed or use upon land vehicles, as well as boats and aircraft. This invention discloses a device of this character which may have a distinctive, penetrating, yet not unpleasant tone that is characterized b definite beats, or in other words, is provided with a heterodyning effect.

Preferably sound-producing units, such as are commonly used in signaling devices, are arranged in conjunction with a common sound conduit having one end closed so that the interaction of the air vibrations produces i a tone with definite beats and undulatory overtones. To this end the sound-producing factors are preferably arranged to have different natural periods of vibrations and may be positioned and arranged in relation to the wall and the sound conduit so that the interaction of the resonant walls with the vibratory? air movement emanating from the sound-producing factors results in a singularly dist1nctive note; it having been found by `25 experiment that the resulting tone may be varied by changing the size, natural period of vibration and position of the sound-producing factors.

` A further object ofthe invention relates to the specific structural combination of sound-producing factors and a sound conduit which permits the manufacture of a distinctive signaling device out of comparatively' inexpensive units, which themselves are separately adapted to use in signaling devices of low cost.

The above and further `advantageous features and objects of the invention will be apparent to those skilled in the art upon a 110 reading of the subjoined description and claims in conjunction with the accompanying drawings, in which Fig. 1 is an elevationalvview of one form of the improved form of sound-producing Fig. 2 is atransverse section shown in Fig. 1; and

Fig. 3 isa transverse sectional view of another ferm of sound-producing device.

The improved soundreducing device, which is exemplified byv Figs. l and 2 of the accompanying drawings, comprises an elongate tubular sound conduit 1 which preferably has one open end and one closed end 2. Preferably this conduit is formed of sheet metal or similar resonant material. Located intermediate the ends of conduit 1 are the sound-producing factors 3 and 4. These factors in the embodiments of the invention illustrated herewith are similar, but differ in size, and preferably are arranged at diiierent distances from the longitudinal axis of the sound conduit 1.

Each of the sound-producing factors comprises a thin vibratory diaphragm 5 through the central portion of which passes a fastening element 6 bearing a disk armature 7 at one end and preferably being provided with a bushing 9 threaded thereon in the region. of the diaphragm, while a plurality of thin reinforcing washers are located directly adjoining the diaphragm. The co-oscillator 12, which preferably is a hollow sheet metal member of annular form, is clamped against the washers upon the outer face of diaphragm '5; this co-osc1llator serves to amplify the air vibration and the sound produced by vibrating the diaphragm. An electromagnet 14 is provided with a core 15 adjoining the armature 9, this magnet beingsecured in conductive relation to the yoke 16 which is secured to the annular plate 17 that is broken away adjoining armature 7. Peripheral portions of the of the device .plate 17 are secured to the diaphragm and to a short sheet-metal passageway 20 which joins the conduit 1 and has its axis disposed substantially in a radial direction in relation to the longitudinal axis of the main sound conduit. The member 20 comprises a peripheral portion 21 which is secured to the from the two factors.

diaplfragm and the plate 17 by fastening elements 22 and a substantially frusto-conical body portion 23 disposed about co-oscillator 12; this portion is connected to conduit 1 by a short tubular member 24. A suitable cover of cup-shaped form may be secured to the sound-producing factor by a. single fasteninO element 29.

luitable make-and-break mechanism is located upon the plate 17 and is designated in general by numeral 30. This mechanism comprises the fixed contact 3l and the contact f 32 mounted upon the spring 33, the end portion of which is located in the path of the armature 7 so that movement of the armature permits alternate making and breaking of an electric circuit for energizing the magnet 14. It is evident that the sound-producing factors 3 and 4 are connected to suitable means for electrical energization thereof, preferably being wired in parallel so that energization of the magnets 14 will result in the attraction of armatures 7 and movement of the diaphragme and co-oscillators toward the magnet, Whereu will be separate the electric circuits will be broken, and the resilience of the diaphragm will tend to return the diaphragms and cooscillators to normal position, the momentum of theseI parts serving to throw them past this position as the electric circuits are again closed. Thus rapid vibration of the diaphragms and co-oscillators results from successive energ1zat1ons of the electromagnets Units 3 and 4 may differ from each other both in the size of the diaphragm and in the size of the electromagnetic energizing means whereby there is a distinct difference in the natural frequencies of vibration and consequently in the pitches of the notes coming Preferably one of the diaphragms is located at a different distance from the axis of the sound conduit 1 than the other diaplelragm. The wall of the sound conduit may provided with an opening 4() if desired which is located substantiall diametrically opposite the diaphragm o one sound-producin unit, such for example as unit 3. It is to e understood, however, that the use of this opening is optional and that its use inerely produces a somewhat dierent tone and acoustic quality in the horn. The units 3 and 4 are preferably located considr erably nearer the closed end of the conduit than the open end thereof. Thus, vibration of the diaphragms and co-oscillators with their different frequencies sets up vibratory Waves in the aircolumn within the conduit, which are reflected from the closed end of the horn and tend still further to provide the device with a distinctive tone.

The form of the invention illustrated 'in Fig. 3 differs from thatllustrated in Figs. 1 and 2, since one of the sound-producing on the contacts 3l and 32l units, such as the factor 4, is located at the end of the sound conduit 101 corresponding to conduit 1 of Figs. 1 and 2, this un'it serving 'to take the place of the closed end of conduit 1. The soundroducing factor 3 is located at one side of t e conduit 101 and is connected thereto by the passage 24 in a manner similar to that previously described. It is evident that the sound-producing units in this form of the invention may be similar to those previously described, and the various parts thereof are accordingly designated by corresponding reference numerals.

It is thus evident that the use of soundproducin units with different frequencies of vibration tends to result in a hetrodyning effect in the air columns within the sound conduit, and the resulting sound is therefore provided' with distinct beats. The diaphragms of the sound-producing units preferably are arranged at right angles to each other so that either unit has little tendency to vibrate in hase with the other unit, although the vi rations emanating from both units are superimposed upon the air column. The arrangement of the units in relation to the resonant walls of the sound conduit and the closed end of the same, whether 4or not this end is closed byv one of the sound-producing factors or merely by a sheet metal wall, not only permits the superimposition of vibrations of different frequencies upon the air column but permits interactionof the same with the echo against the Walls of the sound conduit and the closed end thereof.y

I claim:

1. A signaling device comprising a sound conduit having a closed end and an open end, a pair of sound-producing factors -connected to the conduit, each of said factors comprising a diaphragm and means for vibrating the same, passages between the diaphragms and the sound conduit, one of said diaphragms lying in a plane substantially parallel to the longitudinal axis of the conduit and intersecting the plane of the other diaphragm, the `passage between said diaphragm and the conduit being spaced from the closed end thereof but nearer said end than the open end thereof, whereby a superimposed vibratory e'ect is produced upon the air column within the conduit, not only by the two diaphragms, but also by the reaction of the sound waves against the-conduit wall.

2. A signaling device comprising a sound conduit having a closed end and an open end, a pair of sound-producing factors connected to the conduit, each of said factors comprising a diaphragm and means for vibrating the same, passages between the diaphragms and the sound conduit, one of said diaphragms lying in a plane substantially parallel to the longitudinal axis of the conduit and intersectin the plane of the other diaphragm, said iaphragm being spaced at a greater listance from the longitudinal center of the conduit than the other diaphragm, the assage between said diaphragm and the con uit being spaced from the closed end thereof but nearer said end than the o en end thereof, wherebyla superimposed vi ratory effect is produced upon the a1r column within the conduit, not only by the two diaphragms, but also by the reaction of the sound v waves against the conduit walls.

Signed by me at Lowell, Massachusetts, this sixth. day of June, 1927.

BUTLER AMES. 

